Radio Base Station Apparatus and Radio Communication Method

ABSTRACT

Focused on group directivity reception with respect to a combination between an adaptive array antenna technology and an interference canceller, the present invention is intended to improve the reception characteristic and improve the system capacity by generating a reference signal from the signal after interference elimination, using a difference between the reference signal and the signal after adaptive array antenna reception as an error signal and carrying out group directivity control.

DESCRIPTION

[0001] 1. Technical Field

[0002] The present invention relates to a radio base station apparatusand radio communication method in a digital radio communication, andmore particularly, to a radio base station apparatus and radiocommunication method capable of improving reception characteristics ofuplink signals and increasing the system capacity in a DS-CDMA (DirectSequence-Code Division Multiple Access) system

[0003] 2. Background Art

[0004] In digital radio communications, an adaptive array antenna(hereinafter referred to as “AAA”) technology is used which controlsdirectivities adaptively by adding weights to antenna outputs from aplurality of antenna elements. This AAA technology can suppressinterference signals taking advantage that signals arrive from differentdirections and controlling directivities adaptively. Thus, the adaptivearray antenna technology is an ideal method for eliminating interferencesignals on a same channel.

[0005] On the other hand, in digital radio communications, aninterference canceller technology is used which estimates interferencesignals as well as desired signals based on maximum likelihoodspecifications. This interference canceller technology can eliminateinterference signals from an identical direction, which cannot beeliminated by the AAA technology.

[0006] In recent years, an effort is underway to combine the AAAtechnology and interference canceller technology to make the most offeatures of both technologies. An example of this is a configurationcombining the AAA and a Viterbi equalizer (MLSE: Maximum Likelihoodsequence Estimator) as a non-linear interference canceller (“CascadeConnection of Adaptive Array Least Square Combination and Non-LinearInterference Canceller and Characteristics” (Pukawa et al 1996 Instituteof Electronics, Information and Communication Engineers CommunicationSociety Conference B-406)). In this configuration, the MLSE eliminatesand detects interference signals in an identical direction which cannotbe eliminated by the AAA, but the MLSE involves a problem that theamount of processing grows exponentially with respect to the number ofinterference signals to be eliminated. For this reason, the MLSE isgenerally used as an equalizer intended to eliminate interferencebetween codes that occurs generally depending on the degree of delayedsignals of the own channel.

[0007] However, a CDMA system has generally more multiple channelsreceived at a same time and a same frequency than a TDMA (Time DivisionMultiple Access) system or FDMA (Frequency Division Multiple Access)system or other access systems. In the TDMA system, for example, onlyone channel signal exists in one slot and the own channel delayed signalis the only interference signal (delayed signals of previous slotsignals are also added in high-speed transmission), while in the CDMAsystem, a plurality of channels are code-multiplexed in one slot.

[0008] The AAA in a cellular system is generally subject to restrictionson the number of antennas because of problems involving installation ofantennas and power lines or from the standpoint of costs of its radiosection and signal processing section and though the AAA focusesdirectivities, it actually has a beam width of 10 degrees or more. Forthis reason, it is difficult to spatially separate the AAA from otherchannels completely. Since, as described above, the CDMA system inparticular has more other channel signals in the focused directivitiesthan other access systems, the CDMA system includes more signals to beeliminated by an interference canceller. Thus, combining the AAA andMLSE in the CDMA system results in a problem that the amount of MLSEprocessing will increase exponentially and thereby increase the hardwarescale.

DISCLOSURE OF THE INVENTION

[0009] It is an object of the present invention to provide a radio basestation apparatus and radio communication method capable of improvingreception characteristics of uplink signals and increasing the systemcapacity by combining an AAA and an interference canceller withoutincreasing the hardware scale.

[0010] In view, of the above-described problems, as an interferencecanceller in the CDMA system, and more particularly an interferencecanceller used for a base station apparatus that can know information ofother channels, a multi-user type interference canceller (MUD: MultiUser Detection) is considered to be more advantageous, in terms ofcharacteristics and hardware scale than the MLSE. This is because withthe MUD, the hardware scale grows in proportion to the number N ofchannels to be eliminated but not more than N times.

[0011] However, if each channel receives signals using an AAAindividually, an individual MUD is required according to eachdirectivity, and if the amount of processing of the MUD corresponding toone AAA reception signal (that eliminates interference corresponding toN channels) is assumed to be M, then there is a problem that AAAreception corresponding to N channels will require an amount ofprocessing corresponding to (N direction patterns)×M.

[0012] To solve this problem, it is possible to group a plurality ofchannels (users), group channels in almost identical directions andapply group directivity reception (group weight (GW) reception) forreceiving with an identical directivity (identical weight) to channelsof a same group. In the above-described example, if N=100 and the numberof GWs is 4, the amount of processing 100M becomes 4M, that is, reducedto {fraction (1/25)}.

[0013] The present inventor has come up with the present inventionfocused on group directivity reception with respect to a combination ofthe above-described AAA technology and an interference canceller. Thatis, a main point of the present invention is to generate a referencesignal from a signal after elimination of interference, perform groupdirectivity control using a difference between the reference signal andthe post-AAA reception signal as an error signal and thereby provide atemporal/spatial interference canceller suited to a CDMA system, improvethe reception characteristic and increase the system capacity.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 is a block diagram showing a configuration of a radio basestation apparatus according to Embodiment 1 of the present invention;

[0015]FIG. 2 is a block diagram showing a configuration of aninterference canceller of the radio base station apparatus according tothe above-described embodiment;

[0016]FIG. 3 is a block diagram showing part of a configuration of aradio base station apparatus according to Embodiment 2 of the presentinvention;

[0017]FIG. 4 is a block diagram showing a configuration of a radio basestation apparatus according to Embodiment 3 of the present invention;

[0018]FIG. 5 is a block diagram showing part of the configuration of theradio base station apparatus according to Embodiment 3 of the presentinvention;

[0019]FIG. 6 is a block diagram showing a configuration of a radio basestation apparatus according to Embodiment 4 of the present invention;

[0020]FIG. 7 is a block diagram showing part of the configuration of theradio base station apparatus according to the above-describedembodiment; and

[0021]FIG. 8 is a block diagram showing another example of part of theconfiguration of the radio base station apparatus according toEmbodiment 4 of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0022] With reference now to the attached drawings, embodiments of thepresent invention will be explained in detail below.

EMBODIMENT 1

[0023]FIG. 1 is a block diagram showing a configuration of a radio basestation apparatus according to Embodiment 1 of the present invention.The radio base station apparatus according to this embodiment carriesout group directivity control using a signal subjected to interferencecanceller processing as a reference signal and using a differencebetween the reference signal and the post-AAA reception signal as anerror signal.

[0024] A signal received through antenna 101 is subjected topredetermined radio reception processing (down-conversion and A/Dconversion, etc.) and converted to a baseband signal at radio receptionprocessing section 102. This received data (baseband signal) is sent toweight control circuit 105 and multiplier 103 at the same time.

[0025] Weight control circuit 105 estimates the direction of arrivalfrom the received data and carries out reception weights correspondingto the received data using the result of the direction of arrivalestimation. The weights resulting from the weight calculations areoutput to respective multipliers 103 and multiplied on the receiveddata.

[0026] The signals multiplied by the respective reception weights areadded up at adder 104. The added received data is sent to interferencecanceller 106. Interference canceller (MUD) 106 performs channelestimation from the received data, generates a replica signal of theinterference signal using this channel estimated value, subtracts thereplica signal from the received data and thereby removes theinterference component and obtains demodulated data.

[0027] This demodulated data is sent to reference signal generationcircuit 107. Reference signal generation circuit 107 reconstructs asignal equivalent to the post-AAA received data based on the channelestimated value obtained at channel estimation circuit 108. Channelestimation circuit 108 performs channel estimation based on theinformation from interference canceller 106.

[0028] The signal reconstructed at reference signal generation circuit107 is output to adder 109. Adder 109 receives the post-AAA signal andcalculates a difference between the reconstructed signal, which is thereference signal, and the post-AAA signal. This difference is sent toweight control circuit 105 as an error signal.

[0029] Weight control circuit 105 calculates a reception weight using,the error signal in such a way that this error becomes a minimum. Thereception weight calculated at weight control circuit 105 is output tomultiplier 103, where the received data is multiplied by the receptionweight.

[0030] Then, an operation of the radio base station apparatus in theabove configuration will be explained.

[0031] The signal sent from a communication terminal is AAA-received bymultiplying the antenna output by a reception weight. During this AAAreception, weight control circuit 105 calculates a reception weight andcontrols the reception weight. More specifically, weight control circuit105 estimates the direction of arrival with respect to the receptionsignal (uplink signal) of each channel (user), groups channels based onthe estimation result of this direction of arrival and calculates areception weight for each group (group weight) Here, the receptionweight to form a direction pattern is not limited to the above-describedgroup weight.

[0032] Thus, using a group weight reduces the number of directivitypatterns using reception weights, and can thereby reduce the amount ofcalculation to calculate reception weights. Moreover, since the numberof reception directivity patterns is reduced, the number of replicasignals generated in interference cancellation processing is alsoreduced. This makes it possible to reduce the hardware scale of weightcontrol circuit 105 and interference canceller 106.

[0033] The post-AAA received data is input to interference canceller 106and subjected to interference cancellation processing there. Thisinterference canceller 106 includes a channel estimation/interferencereplica generation unit having a configuration as shown in FIG. 2. Thischannel estimation/interference replica generation unit generates areplica signal of user data, which becomes interference and subtractsthis from the received data and obtains highly reliable demodulateddata.

[0034] The channel estimation/interference replica generation unitincludes channel estimation unit 201 that carries out channelestimation, replica generation unit 202 that generates an interferencereplica using the signal after data decision, RAKE combining section 203that RAKE-combines the channel-estimated signals and data decisionsection 204 that carries out data decision on the RAKE-combined signal.

[0035] Since a plurality of channel estimation units 201 and a pluralityof replica generation units 202 are provided according to the number ofmulti-path reception delayed signals, that is, the number of paths, theinterference canceller can thereby generate an interference replicacorresponding to the respective multi-path reception delayed signals.

[0036] Channel estimation unit 201 includes matched filter 2011 thatperforms despreading processing on the reception signal, channelestimation section 2013 that performs path channel estimation andmultiplier 2012 that multiplies the despread signal which is the matchedfilter output by a complex conjugate of the channel estimated valueestimated at channel estimation section 2013.

[0037] On the other hand, replica generation unit 202 includesmultiplier 2021 that multiplies the data symbol after data decision bythe channel estimated value obtained at channel estimation section 2013and replica generation section 2022 that generates an interferencereplica by reapplying spreading processing to the data multiplied by thechannel estimated value using the spreading code used at matched filter2011.

[0038] For the channel estimation/interference replica generation unitin such a configuration, specific user data is sent to channelestimation unit 201 for every delayed signal. In channel estimation unit201, matched filter 2011 carries out despreading processing on the userdata using a spreading code and obtains a reception symbol.

[0039] The reception symbol obtained through despreading processing is,sent to channel estimation section 2013. Channel estimation section 2013carries out a channel estimation of the user data using a known signalsuch as a pilot symbol and obtains a channel estimated value. Then,multiplier 2012 carries out coherent detection by multiplying theabove-described reception symbol by the complex conjugate of thischannel estimated value. Multiplier 2012, then sends the respectivereception symbols to RAKE combining section 203.

[0040] RAKE combining section 203 RAKE-combines reception symbols of therespective delayed signals and sends the RAKE-combined reception symbolsto data decision section 204. Data decision section 204 carries out datadecision on the RAKE-combined reception symbols and obtains datasymbols.

[0041] The data symbols subjected to data decision are multiplied bychannel estimated values obtained from channel estimation sections 2013of the respective channel estimation units 201 through multiplier 2021of the replica generation unit 202 which is separated at the timing ofeach delayed signal according to the delayed signals.

[0042] The symbol after multiplication is sent to each replicageneration section 2022, where the symbol is subjected tore-spreading/modulation processing using the spreading code used atmatched filter 2011. The re-spread/modulated signals obtained here arecombined into an interference replica signal of the user channel.

[0043] The configuration shown in FIG. 2 is an example of the unit thatcarries out channel estimation and replica generation, but the presentinvention is not limited to this.

[0044] Interference canceller 106 carries out demodulation bysubtracting replica signals of users other than specific user, from thereceived data using interference replica signals obtained at the channelestimation/interference replica generation unit and thereby obtainshighly reliable demodulated data.

[0045] The highly reliable demodulated data obtained atinterference-canceller 106 in this way is input to reference signalgeneration circuit 107, where the post-AAA received data isreconstructed. In this reconstruction, reference signal generationcircuit 107 sends the despread signal despread by a specific spreadingcode at interference canceller 106 to channel estimation circuit 108 andthen performs re-spreading using the specific spreading code used fordespreading using the channel estimated value obtained at channelestimation circuit 108 and generates a replica signal of the post-AAAreceived data.

[0046] A difference between the reference signal of the post-AAAreceived data and actual post-AAA received data is calculated. Thisdifference is sent to weight control circuit 105 as an error signal.This error signal is equivalent to the reception weight error calculatedby weight control circuit 105. Therefore, a reception weight isrecalculated in such a way as to minimize this error. This receptionweight is output to multiplier 103 and multiplied on the received data.As the adaptive signal processing to minimize this error, an LMS (LeastMean Square) algorithm or RLS (Recursive Least Square) algorithm, etc.can be used.

[0047] As shown above, in the radio base station apparatus according tothis embodiment, weight control circuit 105 generates an error signalusing a replica signal and carries out weight control adaptively usingthe error signal, and can thereby perform AAA reception with highaccuracy. In this case, since a replica signal is generated using thesignal subjected to interference cancellation processing, thisembodiment improves the reliability of the error signal and can alsoperform weight control with high accuracy.

[0048] Thus, this embodiment can improve the reception characteristicsof uplink signals. This improves the reception performance of uplinksignals and can thereby reduce transmit power at the communicationterminal, resulting in a reduction of interference in the system and anincrease in the system capacity.

EMBODIMENT 2

[0049] In the radio base station apparatus shown in FIG. 1, interferencecanceller 106 estimates user data channels and generates a replicasignal, channel estimation circuit 108 performs channel estimation forweight control and reference signal generation circuit 107 generates areplica signal.

[0050] Then, as shown in FIG. 3, it is possible to reduce the hardwarescale by rendering reference signal generation circuit 107 thatgenerates a reference signal from a signal subjected to interferencecancellation processing and channel estimation circuit 108 to also serveas the replica generation section and channel estimation section ininterference canceller 106.

[0051]FIG. 3 is a block diagram showing part of a configuration of aradio base station apparatus according to Embodiment 2 of the presentinvention. In this configuration, despreading circuit 301 despreadspost-AAA received data using a specific spreading code and outputs thedespread signal obtained to coherent detection circuit 302 and channelestimation circuit 308.

[0052] Coherent detection circuit 302 carries out coherent detection onthe received data using a channel estimated value obtained from channelestimation circuit 308. The signal subjected to coherent detection isRAKE-combined by combining-circuit 303. This combined signal is sent todata decision circuit 304, subjected to data decision and converted todemodulated data.

[0053] This demodulated data is input to spreading circuit 306 afterbeing multiplied by the channel estimated value at multiplier 305.Spreading circuit 306 applies spreading/modulation processing to thedemodulated data with the channel estimated value multiplied using thespreading code used for despreading and obtains a replica signal. Thisreplica signal is used for interference cancellation processing and atthe same time used as a reference signal.

[0054] That is, a difference between this replica signal and thepost-AAA received data is calculated and this difference is sent toweight control circuit 105 as an error signal. Weight control circuit105 performs weight control in the same way as in Embodiment 1.

[0055] Thus, the radio base station apparatus according to thisembodiment can improve the reception characteristic of uplink signalsand increase the system capacity, and use same interference cancellerfor channel estimation and replica generation and can thereby reduce thehardware scale.

EMBODIMENT 3

[0056] This embodiment describes a modification example of the radiobase station apparatus of the present invention. FIG. 4 is a blockdiagram showing a configuration of a radio base station apparatusaccording to Embodiment 3 of the present invention. In FIG. 4, the sameparts as those in FIG. 1 are assigned the same reference numerals asthose in FIG. 1 and detailed explanations thereof will be omitted.

[0057] First, a modification example of replica signal generation willbe explained. The following three methods are available to generate areplica signal:

[0058] (1) Using only known signal after interference cancellationprocessing (e.g., pilot signal)

[0059] (2) Using provisional decision signal of information data inaddition to pilot signal

[0060] (3) Using output of error correction(FEC)/decoding circuit 401 ordecision data (after deinterleave+error correction(FEC)/decoding ingeneral) when information data section is used

[0061] In this method, a control delay increases, but the reliability ofa replica signal which becomes a reference signal is improved, allowingAAA weight control with higher accuracy.

[0062] Then, a, modification example of group directivity control willbe explained FIG. 5 is a block diagram showing part of a configurationof the radio base station apparatus according to Embodiment 3 of thepresent invention. Channel selection in a group used for replicageneration will be explained using FIG. 5.

[0063] This configuration includes a plurality of channel processingcircuits 501, combining circuit 502 for combining replica signalsobtained at channel processing circuits 501, and channel selectioncircuit 504 for selecting a channel used for replica generation fromvarious information. Reference numeral 503 denotes an adder forcalculating a difference between post-AAA received data and a replicasignal.

[0064] The following five methods are available for channel selection ina group used for replica generation.

[0065] (1) Selecting all channels that belong to a group determined byclassifying a plurality of channels

[0066] (2) Selecting channel according to transmission rate (informationtransmission rate). A channel with a high transmission rate has highsignal transmit power and high power consumption, and therefore it isnecessary to form the best possible directivity to reduce transmit powerthrough transmit power control. Thus, at least one of channels with ahigh transmission rate in the group is selected. This makes it possibleto form better directivity and reduce transmit power through transmitpower control. Thus, interference is suppressed by reducing transmitpower differences from channels with low transmission rates.

[0067] (3) Selecting channel according to distance from communicationterminal, Since a channel of a far communication terminal has hightransmit power and high power consumption, it is necessary to form thebest possible directivity to reduce transmit power through transmitpower control Thus, at least one of channels of far communicationterminals in the group is selected. This makes it possible to formbetter directivity and reduce transmit power through transmit powercontrol. As a result, the load on the communication terminal can bereduced (extending the battery life). Furthermore, when thecommunication terminal is nearer the cell edge (farther from the basestation apparatus), it produces greater interference with other cells,and therefore it is possible to reduce interference with other cellsfrom that point by forming optimal directivity and reducing transmitpower through transmit power control.

[0068] (4) Selecting channel according to number of channels orlikelihood of reception signal (amplitude or power). With regard tolikelihood of a reception signal (amplitude or power), a channel withgreater signal likelihood produces greater interference. On the otherhand, it is easy for such a channel to form correct directivity. Thismakes it possible to form optimal directivity with accuracy and reducetransmit power through transmit power control and reduce interferencewith other channels. Furthermore, with regard to the number of channels,it is possible to reduce the hardware scale by simply reducing thenumber of targets.

[0069] (5) setting parameters according to processing capacity ofinterference canceller (removing up to what extent, etc.) orinstallation environment (whether communication terminals are easilyconcentrated on a same direction or easily distributed uniformly, etc.).These parameters are specific to each apparatus and the installationlocation, and therefore appropriate parameters are selected when eachapparatus is installed.

[0070] By the way, the number of channels can also be selected bycombining these parameters as appropriate.

[0071] In the configuration shown in FIG. 5, channels processing circuit501 of interference canceller 106 generates a replica signal and outputsto combining circuit 502. On the other hand, channel selection circuit504 receives channel information according to the parameters describedin (1) to (5) above, apparatus information of the interference cancellerand installation environment information of the base station apparatus.Channel selection circuit 504 selects a channel to be used for thereplica signal according to the channel information and installationenvironment information, etc. This channel selection information isoutput to combining circuit 502.

[0072] Of the replica signals from channel processing circuit 501,combining circuit 502 combines the replica signals corresponding to theselected channel according to the channel selection information fromchannel selection circuits 504. The combined replica signal is output toadder 503. Adder 503 calculates a difference between the post-AAAreceived data and the combined replica signal. This difference is sentto the weight control circuit as an error signal and subjected to weightcontrol as explained in Embodiment 1. It is also possible to limit thesymbols to be used as a reference signal to only symbols whose receptionsignal likelihood (amplitude or power) is at a level of a certainthreshold or higher from among the selected channels to generate areference signal with higher accuracy.

[0073] Thus, since the radio base station apparatus according to thisembodiment also generates replica signals using signals subjected tointerference cancellation processing, the reliability of an error signalis improved, making it possible to also carry out weight control withhigh accuracy. This makes it possible to improve the receptioncharacteristics of uplink signals. This makes it possible to improve thereception performance of uplink signals and thus reduce transmit powerat the communication terminal and as a result, reduce interference inthe system and increase the system capacity.

[0074] Especially, by selecting a channel for generating a replicasignal, it is possible to reduce the amount of calculation. Also byselecting a channel with high transmit power, it is possible to generatea replica signal accurately and at the same time reduce transmit powerof the channel through transmit power control, and thereby reduceinterference with other stations.

EMBODIMENT 4

[0075]FIG. 6 is a block diagram showing a configuration of a radio basestation apparatus according to Embodiment 4 of the present invention. InFIG. 6, the same parts as those in FIG. 1 are assigned the samereference numerals and detailed explanations thereof will be omitted.

[0076] This embodiment describes a radio base station apparatus thatuses a signal subjected to interference canceller processing and thenerror correction(FEC)/decoding as a reference signal and carries outgroup directivity control using a difference between the referencesignal and a post-AAA reception signal as an error signal.

[0077] The operations after the signal from the communication terminalis AAA-received by antenna 101 until the signal is subjected tointerference cancellation-processing at interference canceller 106 arethe same as that in Embodiment 1.

[0078] The demodulated data subjected to interference cancellerprocessing is sent to de-interleaving circuit 601, deinterleaved thereand sent to error correction(FEC) circuit 602. Error correction(FEC)circuit 602 carries out error correction processing on the deinterleavedand demodulated data. The data subjected to error correction processingis sent to reference signal generation circuit 603. Reference signalgeneration circuit 603 generates a replica signal using the datasubjected to error correction processing. The operations after a replicasignal is generated by reference signal generation circuit 603, adifference between the replica signal and post-AAA received data iscalculated until reception weights are controlled using the differenceas an error signal are the same as those in Embodiment 1.

[0079] Since the radio base station apparatus according to thisembodiment also generates a replica signal using a signal subjected tointerference cancellation processing, it is possible to improve thereliability of an error signal and carry out weight control with highaccuracy. This makes it possible to improve the receptioncharacteristics of uplink signals. Generating replica signals usingsignals subjected to error correction processing will increase controldelays, but also increase the reliability of a replica signal, whichbecomes a reference signal allowing AAA weight control with higheraccuracy.

[0080]FIG. 7 is a block diagram showing a configuration of part of theradio base station apparatus according to this embodiment. In thisconfiguration, the output of interference canceller 106, that is, softdecision data subjected to interference cancellation processing is sentto de-interleaving circuit 7011 of channel processing circuit 701.De-interleaving circuit 7011 applies deinterleave to the demodulateddata after being subjected to interference cancellation processing. Thedeinterleaved demodulated data is sent to error correction(FEC)/decodingcircuit 7012, where error correction codes are decoded.

[0081] The error-corrected received data is sent to errorcorrection(FEC)/coding circuit 7013, where error correction codes arecoded. The data subjected to error correction/coding processing is sentto interleaving circuit 7014 and interleaved there. The interleaved datais sent to modulation circuit 7015 and subjected to modulationprocessing.

[0082] After adder 7016 multiplexes the modulated data with a pilotsymbol, multiplier 7018 multiplies the data by the channel estimatedvalue obtained at interference canceller 106. Then, the data multipliedby the channel estimated value is subjected to spreading/modulationprocessing using the spreading code used at the despreading circuit ofinterference canceller 106 and then combined with delayed signals bycombiner 7019 into a replica signal.

[0083] Each replica signal is sent to combination circuit 702 andcombined there. The combined replica signal is output to adder 703.Adder 703 calculates a difference between the post-AAA received data andthe combined replica signal and outputs the difference to the weightcontrol circuit as an error signal.

[0084]FIG. 8 is a block diagram showing another example of part of theconfiguration of the radio base station apparatus according toEmbodiment 4 of the present invention. This embodiment in thisconfiguration describes a case where the signal obtained by applyingerror correction/decoding to a signal subjected to interferencecanceller processing is used as a reference signal and, groupdirectivity control is performed using a difference between thereference signal and the signal after the interference canceller as anerror signal.

[0085] The operations until deinterleave, error correction/decodingprocessing, error correction/coding processing, interleave, modulationprocessing and multiplexing with pilot symbols are applied to the outputof interference canceller 106, that is, soft decision data subjected tointerference cancellation processing are the same as above.

[0086] This multiplexed data is output to adder 703 as a replica signal.This replica signal is symbol data. The symbol data obtained wheninterference cancellation processing is applied to the post-AAA receiveddata is output to adder 703. Adder 703 calculates a difference betweenthe replica signal, which is the symbol data and the symbol data fromthe interference canceller and sends this difference to the weightcontrol circuit as an error signal.

[0087] Using the replica signal of the symbol data in this way canreduce the processing speed compared to processing in chip units andreduce the hardware scale.

[0088] When decision data after error correction/decoding processing isused as the replica signal, it is also possible to adopt a configurationusing the signal after coherent detection and RAKE combining for all thereplica signal, post-AAA reception signal and error signal.

[0089] Embodiments 1 to 4 above describe the case where the interferencecanceller is an MUD. Examples of MUD include a multi-stage typeinterference canceller in which the receiving side generatesinterference replicas of other users based on estimated reception fadingcomplex envelope and decision data and subtracts this replica from thereception signal, thereby improving an SIR (Signal to InterferenceRatio) for subsequent users and improving the reception characteristic,and a symbol ranking type interference canceller which calculateslikelihood symbol by symbol for all symbols of all users, ranks thecalculation results, generates replicas starting from the symbol withthe highest likelihood, removes these replicas from the input signal,and by repeating all this procedure, improves an SIR with respect toother symbols and thereby improves the reception characteristic.

[0090] The present invention is not limited to Embodiments 1 to 4 above,but can be implemented with various modifications. For example,Embodiments 1 to 4 above can be implemented, combined with one anotheras appropriate.

[0091] The radio base station apparatus of the present inventioncomprises an adaptive array antenna reception section that carries outadaptive array antenna reception processing on a signal from acommunication terminal apparatus, an interference canceller that carriesout interference cancellation processing on the signal subjected to theadaptive array antenna reception processing, a reference signalgeneration section that generates a reference signal of the signal fromthe communication terminal apparatus from the demodulated data after theinterference cancellation processing, and a weight control section thatcontrols reception weights used for adaptive array antenna receptionprocessing using a difference between the signal subjected to theadaptive array antenna reception processing and the reference signal.

[0092] By generating a reference signal using the signal after beingsubjected to interference cancellation processing, this configurationimproves the reliability of an error signal and can also carry outweight control with high accuracy. This makes it possible to improve thereception characteristics of uplink signals. This further makes itpossible to improve the reception performance of uplink signals andreduce transmit power at the communication terminal, thereby reduceinterference in the system and increase the system capacity.

[0093] The radio base station apparatus of the present invention in theabove configuration is also configured with the interference cancellerfurther including a channel estimation section that carries out channelestimation using a signal from the communication terminal apparatus anda replica signal generation section that generates a replica signalusing the signal from the communication terminal apparatus, wherein thereplica signal generation section generates a reference signal using thechannel estimated value.

[0094] This configuration allows the interference canceller to be alsoused to generate reference signals, making it possible to reduce thehardware scale.

[0095] The radio base station apparatus of the present invention in, theabove configuration is also configured to include an error correctionprocessing section that carries out error correction processing on thedemodulated data after interference cancellation processing, wherein thereference signal generation section generates a reference signal usingthe output of the error,correction processing section.

[0096] This configuration makes it possible to select a channel forgenerating a reference signal and reduce the amount of calculation.Selecting a channel with high transmit power makes it possible togenerate a reference signal correctly and reduce transmit power of thechannel through transmit power control, thereby reducinginterference,with other stations.

[0097] The radio base station apparatus of the present invention in theabove configuration is also configured in such a way that a plurality ofcommunication terminal apparatuses is divided into groups based on thedirections of arrival of signals from the communication terminalapparatuses and reception weights are calculated group by group.

[0098] By grouping communication terminal apparatuses for calculation ofreception weights and using weights calculated group by group, thisconfiguration can reduce the number of reception weights. This makes itpossible to reduce the amount of calculation to calculate receptionweights.

[0099] The radio base station apparatus of the present invention in theabove configuration is also configured to include a selection sectionfor selecting a communication terminal apparatus used to generate areference signal from among the communication terminal apparatuses thatbelong to a group.

[0100] This configuration improves the reliability of a replica signal,which becomes a reference signal and allows weight control of anadaptive array antenna with higher accuracy.

[0101] The radio base station apparatus of the present inventioncomprises an adaptive array antenna reception section that carries outadaptive array antenna reception processing on a signal from acommunication terminal apparatus, an interference canceller that carriesout interference cancellation processing on the signal subjected to theadaptive array antenna reception processing, an error correction sectionthat carries out error correction processing on the demodulated dataafter being subjected to the interference cancellation processing, areference signal generation section that generates a reference signal insymbol units of the signal from the communication terminal apparatusfrom the demodulated data after being subjected to the error correctionprocessing, and a weight control section that controls reception weightsused for adaptive array antenna reception processing using a differencebetween the signal subjected to the interference cancellation processingand the reference signal.

[0102] This configuration makes it possible to reduce the processingspeed compared to processing in chip units and thereby reduce thehardware scale.

[0103] The communication terminal apparatus is characterized by carryingout a radio communication with the radio base station apparatus in theabove configuration. This allows the communication terminal apparatus totransmit signals with relatively small transmit power. This makes itpossible to reduce interference of the communication terminal apparatus.

[0104] The radio communication method of the present invention comprisesan adaptive array antenna receiving step of carrying out adaptive arrayantenna reception processing on a signal from a communication terminalapparatus, an interference canceling step of carrying out interferencecancellation processing on the signal subjected to the adaptive arrayantenna reception processing, a reference signal generating step ofgenerating a reference signal of the signal from the communicationterminal apparatus from the demodulated data after being subjected tothe interference cancellation processing, and a weight controlling stepof controlling reception weights used for adaptive array antennareception processing using a difference between the signal subjected tothe adaptive array antenna reception processing and the referencesignal.

[0105] By generating a reference signal using the signal after beingsubjected to interference cancellation processing, this method improvesthe reliability of an error signal and can also carry out weight controlwith high accuracy. This makes it possible to improve the receptioncharacteristics of uplink signals. This further makes it possible toimprove the reception performance of uplink signals and reduce transmitpower at the communication terminal, thereby reduce interference in thesystem and increase the system capacity.

[0106] The radio communication method of the present invention comprisesan adaptive array antenna receiving step of carrying out adaptive arrayantenna reception processing on a signal from a communication terminalapparatus, an interference canceling step of carrying out interferencecancellation processing on the signal subjected to the adaptive arrayantenna reception processing, in error correction processing step ofcarrying out error correction processing on the demodulated data afterthe interference cancellation processing, a reference signal generatingstep of generating a reference signal in symbol units of the signal fromthe communication terminal apparatus from the demodulated data afterbeing subjected to the interference cancellation processing, and aweight controlling step of controlling reception weights used foradaptive array antenna reception processing using a difference betweenthe signal subjected to the interference cancellation processing and thereference signal.

[0107] This method makes it possible to reduce the processing speedcompared to processing in chip units and thereby reduce the hardwarescale.

[0108] As described above, the radio base station apparatus and radiocommunication method of the present invention generate a referencesignal (replica signal) from the signal after interference eliminationand perform group directivity control using a difference between thereference signal and post-AAA reception signal as an error signal, andcan thereby improve the reception characteristics of uplink signals andincrease the system capacity by combining the AAA and the interferencecanceller without increasing the hardware scale.

[0109] This application is based on the Japanese Patent ApplicationNo.2000-009701 filed on Jan. 19, 2000, entire content of which isexpressly incorporated by reference herein.

INDUSTRIAL APPLICABILITY

[0110] The present invention is applicable to a radio base stationapparatus and radio communication method in a digital radiocommunication system, and a DS-CDMA system in particular.

What is claimed is:
 1. A radio base station apparatus comprising:adaptive array antenna receiving means for carrying out adaptive arrayantenna reception processing on a signal from a communication terminalapparatus; an interference canceller that carries out interferencecancellation processing on the signal subjected to said adaptive arrayantenna reception processing; reference signal generating means forgenerating a reference signal of the signal from said communicationterminal apparatus from the demodulated data after being subjected tosaid interference cancellation processing; and weight controlling meansfor controlling reception weights used for adaptive array antennareception processing using a difference between the signal subjected tosaid adaptive array antenna reception processing and said referencesignal.
 2. The radio base station apparatus according to claim 1,wherein the interference canceller further comprises channel estimatingmeans for carrying out channel estimation using the signal from thecommunication terminal apparatus and replica signal generating means forgenerating a replica signal using the signal from said communicationterminal apparatus, and said replica generating means generates areference signal using said channel estimated value.
 3. The radio basestation apparatus according to claim 1, further comprising errorcorrection processing means for carrying out error correction processingon the demodulated data after interference cancellation processing,wherein the reference signal generating means generates a referencesignal using the output of said error correction processing means. 4.The radio base station apparatus according to claim 1, wherein aplurality of communication terminal apparatuses is divided into groupsbased on the directions of arrival of signals from the communicationterminal apparatuses and reception weights are calculated group bygroup.
 5. The radio base station apparatus according to claim 4, furthercomprising selecting means for selecting a communication terminalapparatus used to generate a reference signal from among thecommunication terminal apparatuses that belong to a group.
 6. A radiobase station apparatus comprising: adaptive array antenna receivingmeans for carrying out adaptive array antenna reception processing on asignal from a communication terminal apparatus; an interferencecanceller that carries out interference cancellation processing on thesignal subjected to the adaptive array antenna reception processing;error correction processing means for carrying out error correctionprocessing on the demodulated data after being subjected to saidinterference cancellation processing; reference signal generating meansfor generating a reference signal in symbol units of the signal fromsaid communication terminal apparatus from the demodulated data aftersaid error correction processing; and weight controlling means forcontrolling reception weights used for adaptive array antenna receptionprocessing using a difference between the signal subjected to saidinterference cancellation processing and said reference signal.
 7. Acommunication terminal apparatus carrying out a radio communication witha radio base station apparatus, said radio base station apparatuscomprising: adaptive array antenna receiving means for carrying outadaptive array antenna reception processing on a signal from thecommunication terminal apparatus; an interference canceller that carriesout interference cancellation processing on the signal subjected to saidadaptive array antenna reception processing; reference signal generatingmeans for generating a reference signal of the signal from saidcommunication terminal apparatus from the demodulated data after beingsubjected to said interference cancellation processing; and weightcontrolling means for controlling reception weights used for adaptivearray antenna reception processing using a difference between the signalsubjected to said adaptive array antenna reception processing and saidreference signal.
 8. A radio communication method comprising: anadaptive array antenna receiving step of carrying out adaptive arrayantenna reception processing on a signal from a communication terminalapparatus; an interference canceling step of carrying out interferencecancellation processing on the signal subjected to said adaptive arrayantenna reception processing; a reference signal generating step ofgenerating a reference signal of the signal from said communicationterminal apparatus from the demodulated data after being subjected tosaid interference cancellation processing; and a weight controlling stepof controlling reception weights used for adaptive array antennareception processing using a difference between the signal subjected tosaid adaptive array antenna reception processing and said referencesignal.
 9. A radio communication method comprising: an adaptive arrayantenna receiving step of carrying out adaptive array antenna receptionprocessing on a signal from a communication terminal apparatus; aninterference canceling step of carrying out interference cancellationprocessing on the signal subjected to the adaptive array antennareception processing; an error correction processing step of carryingout error correction processing on the demodulated data after beingsubjected to said interference cancellation processing; a referencesignal generating step of generating a reference signal in symbol unitsof the signal from said communication terminal apparatus from thedemodulated data after being subjected to the interference cancellationprocessing; and a weight controlling step of controlling receptionweights used for adaptive array antenna reception processing using adifference between the signal subjected to said interferencecancellation processing and the reference signal.